> It is equally unlikely for a non-lepidosaur to develop a derived lepidosaur
> trait, as it is for a non-archosaur to develop a derived archosaur trait, so
> no, they probably couldn't be overlapping scales.
As unlikely as a non-dolphin developing a dolphin-like body form
(ichtyosaurs) or a non ornithomimid developing and ornithomid like body
for (ostriches)? Flat overlapping scales developed independantly in
fish and lepidosaurs, and integument developed independantly in birds
and mammals, so what is so strange about flat scales developing
independantly in lepidosaurs and a small dinosaur group? This sort of
independantly derived similarity is what analogy is all about.
> Wrong, wrong wrong!!!!! Mantell was working with an absolute zero fossil
> record and tried to make inferences based on about ten bones. With
> Sinosauropteryx, we are dealing with a huge fossil record showing this
> animal's placement.
None of which gives us any clues as to which of the animals we have
fossils for had feathers and which didn't. Does your logic tell
you exactly when in archosaur history feathers evolved? Does looking at
the fossil bones allow you to say whether it must have evolved in an
early theropod, in the common ancestor of compsognathids and _Archaeopteryx_
or in one even tinier branch of theropods that ultimately lead to
_Archaeopteryx_? Seeing a lot of birdlike characters in theropods may
indicate relationship and ancestry, but it doesn't tell if
particualr traits that weren't preserved in the fossil record had
developed yet. Looking at the bones, there is no more reason to
suppose that feathers were present in the vast majority of theropods than a
pygostyle or keeled sternum. Chimps are more like us phylogenetically and
physically than any other primate, but they don't have protruding
noses, walk urpight most of the time, or do calculus.
I have deep respect for Phil Currie's objectivity, and he personally
examined the fossil, so I do tend to lean toward his interpretation that the
structures are indeed feathers. I'm just saying that the "huge fossil
record" by and large does NOT give us any clues as to exactly when
feathers developed prior to _Archaeopteryx_, and playing the "simple
logic provides the answer game" with a deficit of solid data tends to
provide answers that sound deceptively convincing.
The formal description of _Paleocanimimus_(sp?) and _Sinosauropteryx_
may give us better clues soon enough.
LN Jeff